Enhanced Portable Battery Powered Electrical Appliance

ABSTRACT

An appliance, such as a flashlight, accepts first and second batteries. The appliance also includes an electrical load, such as a light source. A first circuit, such as a DC to DC converter, receives power from the first battery and supplies power to the load. A second circuit, such as a DC to DC converter, receives power from the second battery and supplies electrical power to the load. In one embodiment, the appliance accepts batteries having multiple physical sizes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/705,766, filed Feb. 15, 2010, which is a continuation of U.S.application Ser. No. 11/469,440, now U.S. Pat. No. 7,688,029, filed Nov.8, 2005, which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention finds application to electrical appliances such asflashlights, electrical and electronic devices, medical devices,measurement devices, and other devices which use more than a singlepower source.

BACKGROUND OF THE INVENTION

Primary or non-rechargeable batteries are available in a variety ofphysical sizes, chemistries, and voltages. For example, alkaline andcarbon-zinc primary batteries are commonly available in AAA, AA, C, andD size cells which provide a nominal output voltage 1.5 volts directcurrent (VDC). Secondary or rechargeable batteries are likewiseavailable in a variety of physical sizes, chemistries, and voltages.Examples include lithium ion, nickel metal hydride (NiMH), and nickelcadmium (NiCd) batteries which are available in a range of sizes andvoltages. NiMH and NiCd batteries, for example, are commonly availablein AAA, AA, C, and D size cells which provide a nominal output voltageof 1.2 VDC. Of course, still other battery sizes, chemistries, andvoltages are also available.

Electrical appliances which rely on batteries as a source of electricalenergy are ubiquitous. These appliances perform a variety of functionsand are used in numerous situations, including for example consumer,commercial, industrial, and medical applications. Consequently, portableelectric appliances present a wide variety of electrical loads, such asa light source in the case of a flashlight, sophisticated electroniccircuitry and displays in the case of computing and medical devices,electric motors in the case of devices which produce motion, heating andcooling devices, and the like. Moreover, these devices are packaged inany number of sizes and shapes, depending on the characteristics of theparticular appliance and its application. Generally, however, it isdesirable that these portable devices be readily transportable by ahuman.

The batteries received by these devices are often connected electricallyin series so as to provide the voltage needed to power the load. Whererelatively larger currents are required, two or more batteries (orgroups of batteries connected in series) are sometimes connectedelectrically in parallel.

While such configurations have proven to be extremely useful, they canpresent operational issues. Thus, for example, the mixing of primary andsecondary batteries, partially discharged batteries, batteries havingdiffering charge states, or batteries having different chemistries candeleteriously affect the performance of the batteries and the operationof the appliance. It can also be difficult or impossible to hot swapbatteries during the operation of the appliance.

Another recurring issue is the availability of batteries to power theseappliances. A particularly vexing situation arises when batteries of thesize or type required by a particular appliance are not readily at hand.While an appliance which accepts batteries of more than one size or typeprovides additional flexibility, the mixing of different size batteriescan likewise deleteriously affect the performance of the batteries andthe operation of the appliance.

SUMMARY OF THE INVENTION

Aspects of the present invention address these matters, and others.

According to a first aspect of the present invention, a portable batterypowered appliance selectively receives first and second batteries. Theappliance includes a first electrical load, a first power converterwhich receives power from the first battery and supplies power to thefirst electrical load, a second power converter which receives powerfrom the second battery and supplies power to the first electrical load.

According to another aspect of the present invention, a portable batterypowered appliance includes a housing which selectively receives at leastfirst and second batteries. The appliance also includes a firstelectrical load carried by the housing, a first circuit carried by thehousing and disposed electrically between the first battery and thefirst electrical load, and a second circuit carried by the housing anddisposed electrically between the second battery and the firstelectrical load. The first circuit permits the first battery to supplypower to the first electrical load and prevents the first battery fromreceiving power supplied by the second battery. The second circuitpermits the second battery to supply power to the first electrical loadand prevents the second battery from receiving power supplied by thefirst battery.

According to still another aspect of the present invention, a flashlightincludes a housing which selectively receives a first battery having atleast two physical sizes and a second battery having at least twophysical sizes, a light source, a first DC to DC converter having aninput which receives a voltage provided by the first battery and anoutput which supplies an output voltage to the light source, and asecond DC to DC converter having an input which receives a voltageprovided by the second battery and an output which supplies an outputvoltage to the light source. The outputs of the first and second DC toDC converters are connected electrically in parallel.

According to another aspect, an appliance includes a load, a first powerisolation circuit, and a second power isolation circuit. The first powerisolation circuit generates a first power and isolates the load from thefirst power on the first power being insufficient to independently powerthe load. The second power isolation circuit generates a second powerand isolates the load from the second power on the second power beinginsufficient to independently power the load. The load receives at leastone of the first power and the second power.

Those skilled in the art will recognize still other aspects of thepresent invention upon reading the attached description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a portable battery powered appliance.

FIG. 2 depicts a portable battery powered appliance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a portable battery powered electrical appliance such as aflashlight. The appliance includes a housing 100 which selectivelyreceives two or more batteries 102 ₁, 102 ₂, 102 ₃, . . . 102 _(n). Thehousing 100 also carries two or more power management circuits 104 ₁,104 ₂, 104 ₃, . . . 104 _(n), isolation circuitry 106 ₁, 106 ₂, 106 ₃, .. . 106 _(n), a power switch 108, and an electrical load 110 such as alamp. Also associated with each power management circuit are positive112 p ₁, 112 p ₂, 112 p ₃, . . . 112 p, and negative 112 n ₁, 112 n ₂,112 n ₃, . . . 112 n _(n) electrical contacts.

Each power management circuit 104 is electrically connected to acorresponding battery 102 and preferably includes a direct current todirect current (DC to DC) converter which converts the input voltageprovided by the corresponding battery to a desired output voltage.

Each power management circuit 104 is configured to accept an inputvoltage or voltage range appropriate to the battery 102 at its input. Inone embodiment, the power management circuit 104 accepts input rangingfrom about 0.9 to 5.5 volts direct current (VDC). Such an arrangement isparticularly suitable where the appliance is configured to acceptbatteries 102 of multiple chemistries or where the batteries 102 mayinclude more than one cell or battery connected in series. Alternately,each power management circuit 104 may be configured to accept a singlenominal input voltage or a relatively limited range of nominal inputvoltages, for example nominal input voltages in the range ofapproximately 1.2 to 1.5 volts direct current (VDC). Such an arrangementis particularly well suited to situations in which the housing 100 isconfigured to accept one or more of D, C, AA, or AAA size cells. Ineither case, the power management circuits 104 are preferably configuredto also operate with input voltages somewhat below the nominal inputvoltage to allow for continued operation as the battery or batteries 102discharge. Different nominal input voltages and voltage ranges are alsocontemplated.

The power management circuits 104 are configured to provide an outputvoltage appropriate for the load 110. Depending on the characteristicsof the batteries 102 and the requirements of the load 110, the powermanagement circuits 104 may function as step-up converters, step-downconverters, or both. The power management circuits 104 may also producean output voltage which is approximately the same as the nominal batteryvoltage. In any case, the power management circuits 104 are preferablyconfigured so that each produces the same nominal output voltage. It isalso desirable that the power management circuits 104 include closedloop feedback or otherwise provide at least a degree of voltageregulation at their respective outputs. While optional, such aconfiguration is particularly useful where it is desirable to presentthe load 110 with a nominally constant voltage, even as one or more ofthe corresponding batteries 102 discharge, or where the power managementcircuits 104 are configured to accept a range of input voltages.

Each power management circuit 104 preferably also includesstate-of-charge detection circuitry which detects the charge state ofthe corresponding battery 102. In one embodiment, the state-of-chargedetection circuitry disables the power management circuit 104 if thecorresponding battery 102 becomes discharged, is not installed, or ifthe battery's output voltage otherwise falls below a threshold voltage.One or more human readable indicators 105 ₁, 105 ₂, 105 ₃ . . . 105 _(n)such a liquid crystal display, light emitting diode, or beeper or otheraudible device in electrical communication with the state-of-chargedetection circuitry may also be provided to indicate the charge state ofthe batteries 102. In addition to or instead of providing a binarycharged/discharged indication, the indicators may also indicate therelative charge state of the batteries 102. The indicator or indicatorsare preferably carried by the housing 100 in a location where they canbe seen, heard, or otherwise perceived by the user. Where the load 110otherwise includes a human readable display, the indicator functionalitymay also be performed by the display.

One suitable implementation of the power management circuits 104 isbased on the Max1705 DC to DC converter integrated circuit availablefrom Maxim Integrated Products, Inc. of Sunnyvale, Calif. Otherimplementations are contemplated.

The outputs of the various power management circuits 104 are connectedelectrically in parallel to create what can be visualized as a commonvoltage bus or connection 114. Disposed between each power managementcircuit 104 and the voltage bus 114 is an isolation circuit 106 such asa field effect transistor, diode, or the like. The isolation circuitisolates its corresponding power management circuit 104 in case thepower management circuit 104 is disabled or otherwise is not producingthe desired output voltage. More particularly, the isolation circuits106 prevent current supplied by other power management circuits 104 fromflowing into any other given power management circuit 104.

The switch 108 controls the application of power to the load 110. In oneembodiment, the switch 108 is operated manually by the user. In the caseof a flashlight, the load may be implemented as one or more lightemitting diodes, incandescent lamps, or other suitable light source(s).Other loads are also contemplated, depending on the function andapplication of the particular appliance. As will be appreciated,appliances and their loads 110 can have a wide variety of applicationand take any number of forms. Examples include, by way of example andnot limitation, consumer, industrial, commercial, and medicalapplications. Similarly, the loads 110 may include, by way of exampleand not limitation, electrical and electronic circuitry, devices whichproduce heat or cooling, and motors and other devices which generatemotion. Depending on the characteristics of the load, it may also bedesirable to integrate some or all of the power management circuits 104with the load 110, for example by integrating some or all of therequired functionality in one or more application specific integratedcircuits (ASICs).

As noted above, the output voltage of the power management circuits 104is established based on the voltage required by the load 110. Inaddition, the number and type of batteries 102 to be accepted by theappliance and the characteristics of the power management circuits 104are established as a function of the power requirements of the load 110.In a first implementation, the load 110, batteries 102, and powermanagement circuits 104 are selected so that any one of the batteries102 and power converters 104 are sufficient to independently power theload 110. In a second implementation, at least n+1 batteries 102 andpower management circuits 104 are provided, where n is the number ofbatteries 102 and circuits 104 needed to power the load 100. In a thirdimplementation, n batteries 102 and power management circuits 104 areprovided.

As the first implementation provides substantial redundancy and isespecially conducive to hot swapping of multiple batteries 102, it isespecially well suited to applications where reliability is particularlyimportant. The second implementation facilitates limited hot swappingand provides a degree or redundancy while being relatively more spaceefficient than the first implementation. The third implementation isespecially well suited to applications where space efficiency isparticularly important.

In the second and third implementation, the appliance 100 may alsoinclude load sharing circuitry to equalize the load carried by thevarious batteries 102 and power management circuits 104.

Where the characteristics of the load 110 are such that it requires aparticular operating current, the power management circuits 104 may beimplemented as voltage to current converters. The outputs of the variouspower management circuits would then be connected electrically in seriesto provide what can be visualized as a common current bus.

The detailed mechanical configuration of the housing 100 is a functionof the characteristics and application of the particular appliance andmay be readily implemented by one skilled in the art based onapplication-specific requirements. In one implementation, the housing100 includes a number of battery receiving regions or apertures, each ofwhich is configured to receive a battery or batteries of a relativelylarger size, for example D-size cells. Should the user wish to use asmaller battery, a battery adapter or shell can used to adapt thesmaller battery to fit in the housing. In another implementation, eachregion is configured to receive a battery or batteries of a particularsize, for example AAA, AA, C, or D size cells. In still anotherimplementation which is useful where physical size is particularlyimportant, each region is configured to receive batteries having a rangeof sizes, for example two or more sizes selected from the group of AAA,AA, C, and D size cells. Each receiving area then includes adjustableelectrical contacts and mechanical support arrangements suitable for thedesired battery sizes, in which case batteries having the desired sizecan be inserted by the user as needed. Other sizes and combinations ofsizes are also contemplated. In applications in which hot swapping isimportant, the housing 100 is arranged to facilitate access to thebatteries 102.

FIG. 2 depicts a further arrangement for a portable battery poweredelectrical appliance.

The appliance includes a housing 100 which receives two or morebatteries 102 ₁, 102 ₂, 102 ₃, . . . 102 _(n). The appliance alsoincludes corresponding power management circuits 104 ₁, 104 ₂, 104 ₃, .. . 104 _(n) and one or more electrical loads 110 ₁, 110 ₂, 110 ₃ . . .110 _(p), a secondary battery 202, and charge control circuitry 204.

The power management circuits 104 each accept power from one or morebatteries 102 through associated contacts 112 p, 112 n. While FIG. 2depicts each battery 102 as comprising only a single battery, multiplebatteries may also be connected electrically in series or parallel. Theoutputs of the power management circuits 104 are connected electricallyin parallel with the voltage bus 114.

Each power management circuit 104 isolates its respective battery 102from the voltage bus. More particularly, each power management circuit104 permits its corresponding battery 102 to supply power to the load110 but prevents an inflow of current from other batteries 102 if itscorresponding battery becomes shorted, relatively more discharged, orthe like. Depending on the characteristics of the batteries 102 and theload, 110, the power management circuits 104 may also provide DC to DCconversion, voltage to current, or other power conversion functionalityas described above in FIG. 1. State of charge detection circuitry and ahuman readable state of charge indicator 105 are also preferablyassociated with each power management circuit 104.

The electrical loads 110 ₁, 110 ₂, 110 ₃ . . . 110 _(n) are electricallyconnected to and receive power from the voltage bus 114. In the case ofa flashlight, for example, each load 110 may include one or more lightsources such as LEDs. Again, other loads are also contemplated,depending on the function and application of the particular appliance.

In one embodiment, the appliance includes electrical connectors andmechanical mounting arrangements which allow one or more of the loads110 to be selectively installed or removed from the appliance. Such anarrangement is particularly advantageous in applications where hotswapping or replacement of the loads 110 is required, where it isdesirable to readily configure the appliance with different loads 110,or it is otherwise desirable to readily change one or more of the loads110.

In addition, and depending on the requirements of a particularapplication, a power switch may be associated with each load 110.Alternately, some or all of the loads 110 may share a common powerswitch, or some or all of the loads may be unswitched.

The appliance may also accept one or more secondary batteries 202.Bidirectional charge control circuitry 204 connected to the voltage bus214 controls the charging and discharging of the secondary battery 202.More particularly, the charge control circuitry 204 supplies therequisite energy to charge the secondary battery when sufficient voltageis present on the voltage bus 114. When sufficient voltage is notpresent on the bus 114 (for example when one or more of the batteries102 is missing or discharged), the secondary battery 202 powers thevoltage bus 114.

The appliance may also include electrical connections for receivingpower from an external source 250 such as a low voltage power supply orpower cube connected to the alternating current (ac) power mains. Someor all of the power supply functionality may also be included in theappliance 200. Such arrangements facilitate charging of the secondarybattery 202 and also extend the life of the batteries 102 in situationswhere the appliance is operated from a fixed location.

Moreover, the one of the loads 110 may be a power converter 104 of asecond battery powered appliance, one example being the flashlight ofFIG. 1. In that case, both appliances would include suitable electricalconnections for removably connecting the voltage bus 114 of the firstappliance with the input of one or more of the power converters 104 ofthe second appliance. Such a configuration provides additionalflexibility in cases where the user does not have a battery for use withthe second appliance or wishes to power the second appliance from thefirst, for example when the first appliance is powered from an externalsource.

Again, the mechanical configuration of the housing 100, as well as thenumber and type of batteries 102, power management circuits 104, and thenumber and characteristics of the loads 110 are readily establishedbased on the requirements of a particular application.

In operation, the user installs the desired batteries 102. Each powermanagement circuit 104 draws power from is respective battery 102 (orbatteries) and presents power to the load. Where the power managementcircuits 104 comprise DC to DC converters, each power management circuit104 provides the desired DC voltage at its output and hence providespower to the load. As each battery 102 discharges, or if the power drawnby the load 110 changes, the respective power management circuit 104preferably maintains its output at a substantially constant voltage.

When a particular battery 102 becomes discharged, the respectiveisolation circuit 106 isolates the particular power management circuit104 and the battery 102 from the other power management circuit(s). Therespective state of charge indicator 105 alerts the user of the need toreplace the battery 102. Provided that the remaining battery (orbatteries) 102 and power management circuit(s) are sufficient to powerthe load 110, operation of the load 110 continues unaffected.

The user then replaces the discharged battery 102 with another batteryof a type which is accepted by the appliance. Where reliable operationof the load is particularly important, the user may also elect toreplace one or more of the batteries before they become fullydischarged. For example, if the appliance receives batteries of morethan one size, the user may replace the battery 102 with a size that itis readily available, even if it is of a different size than thosealready installed or the one it is replacing. Even where the applianceaccepts batteries having a single size, the user may replace thedischarged battery 102 with another battery of the same size, eventhough its charge state may be uncertain or the batteries are ofdifferent chemistry.

Where the appliance includes a secondary battery 202 and charge controlcircuit 204, the secondary battery 202 is charged from voltage availableon the bus 114. Where one or more of the batteries 102 becomedischarged, are not installed, or are otherwise insufficient to powerthe load 110 such as in the case of relatively higher peak loads, thesecondary power 202 likewise supplies power the bus 114 and hence theload 100.

Also, where the appliance contains suitable connectors and mechanicalarrangements, the user may install, remove, or replace one or more ofthe loads 110 during operation of the other appliance.

The invention has been described with reference to the preferredembodiments. Of course, modifications and alterations will occur toothers upon reading and understanding the preceding description. It isintended that the invention be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims.

1. An appliance comprising: a load; a first power converter whichgenerates a first power from a first received power; a first powerisolation circuit that isolates the load from the first power on thefirst power being insufficient to independently power the load; a secondpower converter which generates a second power from a second receivedpower; a second power isolation circuit that isolates the load from thesecond power on the second power being insufficient to independentlypower the load; and wherein the load receives at least one of the firstpower and the second power.
 2. The appliance of claim 1, wherein thefirst power isolation circuit comprises isolation circuitry toselectively isolate the first power form the load.
 3. The appliance ofclaim 2, further comprising a first battery to generate the firstreceived power.
 4. The appliance of claim 1, further comprising a firstbattery to generate the first received power.
 5. The appliance of claim4, further comprising a second battery to generate the second receivedpower.
 6. The appliance of claim 5, wherein the second power converteryields the second power at a voltage varied from the second battery. 7.The appliance of claim 1, further comprising a state of charge circuitcoupled to the load and the first power isolation circuit thatdetermines a state of charge.
 8. The appliance of claim 7, furthercomprising an indicator to indicate the state of charge.
 9. Theappliance of claim 1, wherein the second power isolation circuitprevents the first power from flowing into the second power isolationcircuit.
 10. The appliance of claim 1, further comprising load sharingcircuitry that equalizes the first power and the second power.
 11. Theappliance of claim 1, further comprising a secondary battery and chargecontrol circuitry coupled to the secondary battery and the load.
 12. Theappliance of claim 11, wherein the charge control circuitry charges thesecondary battery utilizing at least one of the first power and thesecond power.
 13. The appliance of claim 11, wherein the charge controlcircuitry provides third power from the secondary battery to the load.